In our previous papers, some theoretical investigations on the strength of container ships were reported. But, last year, the torsional strength test on the actual container ship “Hakone Maru” was carried out in order to confirm the reliability of the above torsional strength theory. In this paper, the results of the above experimental test are described. And the following results are obtained. 1) The torsional distortion of hatch opening can be estimated by the theoretical calculation which was introduced in our previous papers. 2) The position of shear center of the vessel is considered to be at the near the base line of ship. 3) The stress distribution of hatch corner can be estimated theoretically based on four elemental stresses due to torsional distortion of hatch, longitudinal bending and horizontal bending of upper deck and axial force of cross deck, respectively.